I have the same issue with my iMac late 2015 [https://www.ifixit.com/Answers/View/500477/iMac+won't+start+up.+No+diagnostic+LEDs.+PSU+tested+fine+(see+.+below)]
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I want to upgrade Hard Drive, the symptom are the same...
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I want to upgrade the Hard Drive, the symptom are the same...
no diag LED's at all...
The power supply has been replaced, unsuccessfully ...
The 12Vdc come on logicboard from the big bottom connector. But it seems that there are MOSFET's that are not triggered
Do you have pinout of the litlle black connector on top and tension on this little 7pins connector
Hello MAharaja,
Same issue with my imac late 2015 / want to upgrade Harddrive / the symptom are the same...
no diag led at all...
the powersupply has been replaced ...unsucessfuly...
the 12Vdc come on logicboard from the big bottom connector but .... seems that there are mosfet that are not triggered
do you have pinout of the litlle black connector on top and tension on this little 7pins connector
Annabelle